Preparation and characterization of a new C18 urea phase based on titanized silica

A new stationary phase containing embedded urea groups (-NH-C(O)-NH-) was prepared by a procedure based on the synthesis of a trifunctional C18 urea-alkoxysilane, followed by modification of titanized silica and further endcapping to evaluate if the embedded group would minimize the higher retention and tailing for basic compounds seen with C18 titanized silica phases. Infrared, 13C and 29Si spectroscopies were employed to characterize the C18-urea titanized silica phase. Chromatographic evaluations used hydrophobic, polar and basic compounds to verify the effects of the polar urea groups embedded in the C18 urea phase. The chromatographic parameters, especially for the separation of basic compounds, compare favorably with those obtained on a C18 titanized silica stationary phase, prepared by silanization of titanized silica with octadecyltrimethoxysilane.